In a 10-minute hearing held amid tight security, Abu Khattala spoke just two words, both in Arabic. He replied “yes” when asked to swear to tell the truth and “no” when asked if he was having trouble understanding the proceeding.

A grand jury indictment handed up under seal Thursday and made public Saturday said Abu Khattala participated in a conspiracy to provide material support and resources to terrorists in the attacks of September 11, 2012, that killed U.S. Ambassador Chris Stevens and three other Americans.

The government said it soon would file more charges against Abu Khattala.

Khattala, a leader of the terrorist organization Ansar al-Sharia, has previously denied any connection to the Benghazi attack. He was captured by U.S. special forces in Libya two weeks ago, marking the first breakthrough in the investigation.

Officials had been questioning Abu Khattala aboard a Navy ship that transported him to the United States, reported AP.

His capture was seen as a victory for President Barack Obama, who has been accused by Republicans of playing down the role of Al-Qaeda in the 2012 attacks for political reasons and being slow to deliver on promises of justice.